In the field of electrical power measurement, many kinds of electrical power meters are known. However, prior art apparatus have been dimensioned with regard to electromechanical measuring devices. This has led to bulky devices, which are difficult to install.
The UK patent document GB-2 321 305 discloses a remote meter reading apparatus provided for retrofitting to an existing meter. This reading apparatus relies on an already installed meter having a Ferraris disc. The apparatus is provided with a wireless transmitter for transmitting data derived from a sensor to a remote location. However, this solution provides for a bulky device limited to its application in existing networks.
An electronic meter or measuring electrical power fed from an electrical power distribution network to an electrical power consumer itself requires electrical power in order to function. A convenient way of providing this power is to furnish the electronic meter with means for drawing electrical power from the power network used to supply the consumer. However, the current which an electronic meter is permitted to draw from an electrical power distribution network is limited by statutory regulation.
The UK patent document GB-2 301 903 discloses an electrical power supply meter provided with an opto-transmitter arranged for communicating data appertaining to a meter reading and at the same time not to disturb the power network connected to the meter.
Trip units for tripping an electronic circuit are known for example through the European patent document EP 0 949 734-A2. In the device disclosed therein processors are arranged to trip an electric circuit on detection of a fault condition. However, there are other instances where tripping of an electric circuit is desired.